Just based on my uninformed prejudices, I would go with Donaldson, Wix, and Baldwin in that order. All three are probably fine though. I think that Napa is made by Wix. As you mention, Fram does not usually do well in tests.

Just got back from getting my filters at Napa, locally they have their Gold Filter sale going on. Got my fuel filters for $4.76 and $4.91 and the oil filter for $2.78 Got my 4 air filters for $10.31 each. All set for my yearly service.

With the new Detroits 50,000mi oil change, Baldwin filters had a tendency towards falling apart before the 50,000mi. I would think that might also apply to a bus sitting for several weeks at a time. Good Luck, TomC

I'm curious Jim, what kind of air filter are you using? Reason I ask is that the Donaldson ECO series , once installed should last darn near a lifetime at the miles we put on our motorhomes if you don't run off road. I run one on the Eagle with a filter minder (which I am somewhat skeptical of) and also have one on the Silverside. Just wondering.

I don't think that any of us have to worry about the quality of a name brand filter. To me it's the same as Ford vs Chevy.These filters are manufactured to handle heavy equipment in harsh conditions. We are neither.

I use Wix as they were recommended by Prevost. I know I over kill on oil maintenance but I chage the oil and filters at 5000 miles. With the low mileage per year I believe it is the single best maintence thing that I do. I try to do the service in the spring so as to get any condensation and have it fresh for the summer. I also always have Detroit desiel do an oil analysis. They have maintained records on my coach for years and are a good way to catch any early problems.

My current air filter is a Wix 46883 and that crosses to the Donaldson (above). This is the filter for the Freightliner I got the first engine from. I took the cowl mount housing and modified it for the bus. I am using the standard passenger side Eagle opening (larger than standard for the Houston Metro buses). I looked a while back and that filter has among the highest flow ratings as I recall.

I also use a filter minder and it always reads fairly high restriction. That said, the filter generally has a large amount of dust (I don't take it on dirt roads, but the pull outs often have loose dirt that is kicked up by the bogies and rear wheels) after each trip. I blow out the dust with open ended 3/8 DOT tubing.

For a long time, I have wanted to put a water manometer on both the intake and exhaust sides of the engine - can't seem to find the time to hook up a simple jury-rigged system. The priority drops down when I consider how strongly the engine pulls - doesn't seem like it could be too bad. In addition, making either end of the system more free-flowing would be a major modification.